Extrusion of metal



A. B. GRAHAM EXTRUSION OF METAL May 15, 1962 2 Sheets-Sheet 1 Filed Aug.4, 1958 ALEXANDER B. GRAHAM INVENTOR.

ATTORNEY y 1 1962 A. B. GRAHAM 3,034,642

EXTRUSION 0F METAL Filed Aug. 4, 1958 2 Sheets-Sheet 2 w LTLH% n IO C :3f m 0) N 2 LL ALEXANDER B. GRAHAM INVENTOR.

ATTORNEY 3,034,642 EXTRUSION F METAL Alexander Barbour Graham,Whitecraigs, Glasgow, Scotland, assignor to The International NickelCompany, lino, New York, N.Y., a corporation of Delaware Filed Aug. 4,1958, Ser. No. 752,334 Claims priority, application Great Britain Oct.11, 1957 2 Claims. (Cl. 207-9) The present invention relates toextrusion of metal, and more particularly to a special extrusion die andapparatus for extruding hard, refractory metals and/or alloys, toimprove the quality of the extruded surface thereof and to a process foraccomplishing the same.

As is well known to those skilled in the art, relatively soft metals andalloys such as aluminum, tin, lead, zinc, brass, etc., generally can beextruded with facility in accordance with modern techniques. However,extrusion of hard, refractory, difiicultly workable metals and/or alloyspresents problems not normally encountered in extruding thecomparatively soft metals such as those enumerated above. For example,the hardness of refractory metals, e.g., nickel alloys, necessitates theutilization of extremely high pressures, e.g., over 100,000 pounds persquare inch (p.s.i.) being not uncommon, and temperatures, e.g., 900 C.(1652 F.) to upwards of 1300 C. (2372 F.), in order to achieve thenecessary state of plasticity for deformation of the material duringextrusion, A a consequence of such high pressures and temperatures,there is undue wear on the dies necessitating frequent replacement andthe extruded pieces have been prone to exhibit surface defects.

One of the primary surface defects characteristic of extruded hard,refractory metals and/or alloys is oxide scale. As a consequence of thehot working procedures employed to bring the metal to extrusiontemperature, the metal is in a condition in which it is inherently proneto the development of surface oxides. Of course, such oxides must beremoved from the extruded piece and it is not difficult to appreciatethe significant loss of metal incurred in removing the oxides,particularly when it is considered that extrusion ratios of 40 or 60 to1 are not uncommon in practice. Moreover, the severe extrusion pressuresexerted tend to promote a deeper penetration of the contaminating oxidesinward of the longitudinal axis of the extruded piece which necessitatesremoval of a section of greater thickness than might be the case inother metallurgical operations. The removal of surface oxides from theextruded product is not a simple task and often requires expensive andtedious operations, e.g., scalping, chipping, grinding, turning, etc.

Heretofore, the art has endeavored to obviate the problem by recourse toelaborate and varied precautionary measures directed to the preventionof the formation of surface oxides prior to the extrusion operation. Forexample, during the course of pro-heating a billet of hard, refractorymetal furnace temperatures and atmospheres are carefully controlled.Such procedures entail the use of special and sensitive apparatus toinsure, for example, the provision of a reducing atmosphere in thefurnace. Special furnaces, e.g., low frequency induction furnaces, h vealso been proposed to meet the problem. Even with the use of such costlyprocedures or special apparams, the metal too often exhibits surfaceoxide defects immediately prior to extrusion. When the metal billets areshaped by extrusion, the oxidized surface layers and other surfacedefects on the billet cause defects to appear on the surface of theextruded product and cause increased die wear. If the metal to beextruded is soft, e.g., brass, this drawback of surface oxidecontamination is commonl avoided by using a ram which cuts through themetal and leaves a thin stocking of the billet metal in the extrusioncontainer, the oxidized layers and surface defects being in thisstocking. If, however, the metal is of a hard refractory nature, thisconventional method is not practicable, as the rim on the ram will notwithstand the wear involved.

Although many attempts were made to overcome the foregoing diflicultiesand other disadvantages, none, as far as I am aware, was entirelysuccessful when carried into practice commercially on an industrialscale.

It has now been discovered that billets or ingots of metal and/oralloys, particularly hard, refractory metals and/or alloys, havingsurface defects such as oxide scale can be extruded such that theextruded product is characterized by markedly improved surface qualitiesthrough the utilization of a novel extrusion die having specialstructural features.

It is an object of the present invention to provide an extrusion processfor improving the surface quality of the extruded product.

Another object of the invention is to provide a novel extrusion die ofspecial configuration for enhancing the surface quality of the extrudedmetal and/ or alloy.

The invention also contemplates providing an extrusion process and dieof special structure for improving the surface quality of extruded hard,refractory metals and/ or alloys.

It is a further object of the invention to provide an extrusion processand die which remove surface defective metal from and impart improvedsurface qualities to the metal extruded. The invention furthercontemplates an extrusion apparatus for accomplishing the foregoing.

Other objects and advantages will become apparent from the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIGURE 1 is an axial sectional view through an illustrative extrusionpress featuring the special die structure of the invention; and

FIGURE 2 depicts a section similar to FIGURE 1 showing a differentworking position.

Generally speaking, the present invention contemplates a die of novelstructural configuration and a process and apparatus for extrudingmetals and/or alloys, particularly hard, refractory metals and/oralloys, having surface defects, e.g., oxide scale. In accordance withthe invention, the skin of the billet to be extruded and which containsthe surface defects is extruded simultaneously but apart from thedesired product. This is accomplished by providing a second diesurrounding the first to leave a continuous narrow annular space at theend of and just inside the wall of an open end container. The dies arecorrelated structurally to cooperatively form a continuous anduninterrupted annular orifice substantially concentric to the productdie orifice and adapted to remove the surface skin from the billet oringot during the extrusion thereof. It is most advantageous that theinternal radius of the wall of the annular orifice be substantially thesame as the interior wall of the extrusion container or chamber tothereby form therebetween an uninterrupted surface.

In accordance with the invention, hard, refractory metals includingnickel, chromium and cobalt and alloys thereof such as nickelchromiumalloys, nickel-chromiumiron alloys, nickel-chromium-cobalt alloys,cobalt-chromium alloys, stainless and heat-resisting steels, etc, havingsurface defects, e.g., oxide scale, can be satisfactorily extruded.

For the purpose of giving those skilled in the art a betterunderstanding of the invention and/or a better appreciation of theadvantages of the invention, reference is now made to the drawings whichillustrate, by way of example, a preferred embodiment of the extrusiondie assembly in operation in accordance with the invention.

Referring to FIGURE 1, there is shown a cylindrical Patented May 15;,1962 billet B inserted in a cylindrical open end container 1 of anextrusion press. The container 1 is surrounded by a housing 2 which isin contact with a second housing 3. At the forward end of the containerthere is a circular product die 4 with a central opening and an annulardie 5 which surrounds the die 4 and, as shown, is of the same internalradius as the container 1. It will be noted that the substantiallyconcentric die structure, as described, provides a continuous anduninterrupted annular scalping orifice 25 through which the surfacedefective skin of the metal to be extruded passes. Moreover, since theinternal radius of the annular die is the same as the radius ofcontainer 1, there is provided an uninterrupted and smooth passage wallfor extruding the skin 14 which, as mentioned hereinbefore, isadvantageous for achieving highly satisfactory results.

The die 4 is carried by a holder 6 which, as shown, is bolted to anannular block 7 which lies in a circular opening in the housing 3. Thecoupling between the die 4 and the holder 6 is shown by way ofillustration as the breech-block type and is made or broken by relativerotary movement of the holder and die.

Annular die 5 is held in position in a recess in the housing 2 andagainst the container 1 by an annular plate 8 which is bolted to thehousing 2.

The block 7 is engaged by and can be moved axially by a tube 21 operatedby, for example, hydraulic means. When block 7 is in the operatingposition shown, it is held by two opposed blocks 9 slidable into andpartly out of cylinders 10 in the housing 3.

The two dies 4 and 5, the plate 8, the block 7 and the holder 6 areshaped to form an annular cavity or passage 11 in communication with theannular space (orifice) between the dies. Preferably, the annularpassage 11 has a closed end, i.e., is a blind passage, as shown inFIGURE 1. Communicating passage or cavity 11 can be advantageously offrustro-conical configuration, as shown, although other suitableconfigurations may be employed.

When the billet is forced to the left as, for example, by ram 12, someof the metal is forced through the die 4 to emerge as the desiredextruded product 13, and the skin 14 of the billet passes through theannular opening (orifice 25) between the dies 4 and 5 into the blindcavity 11. The free end of the skin metal can strike the blind end ofthe cavity or passage and buckle more or less as shown at 15 if theoriginal billet is long. This advantageously provides for extrudingrelatively long billets and eliminates otherwise premature disassemblyof the apparatus.

At the end of the extrusion operation the blocks 9 supporting the block7 are withdrawn at right angles to the line of extrusion. The wholeassembly of the block 7, holder 6 and die 4 can be withdrawn byoperation of the tube 21. There is, of course, some of the originalbillet still in the container 1 as a discard 16, and if this should bewedged in the container the main ram 12 may also be used to assist themovement from the position shown in FIGURE 1 to that shown in FIGURE 2.

It is a further advantageous feature of the invention that the discard16 and the skin 14 which is attached to it can both be readily disposedof while simultaneously separating the extruded product therefrom in asingle operation. This is achieved by gripping the discard in adouble-acting vise, each jaw 17 being operated by suitable means such asa hydraulic ram. Next the die assembly is moved back while the discardis still held by the vise, and then a circular saw 18 driven by a motor19 carried by a support 20 is brought into action. The support 20 isguided to slide and is moved hydraulically inwards to cause the saw tocut through the skin 14 and the product 13.

In the application of the invention to heat-resisting andcreep-resisting alloys such as those having a nickelchromium base, glassmay be used as a lubricant, a pad of glass fiber being inserted betweenthe billet and the die 4, and further glass fiber being interposedbetween the billet and the wall of the container 1.

The thickness of the skin 14 can of course be regulated by varying thewidth of the annular space between the dies 4 and 5 and by this meansalso the total extrusion ratio is varied. By thus reducing the ratio, itis possible to produce from a billet of given diameter a product of muchsmaller cross-sectional area than would be possible if the skin were notextruded through the outer annular orifice in accordance with thepresent invention.

The present invention is particularly applicable to the extrusion ofbillets and/or ingots made from hard, refractory and difficultlyworkable metals and/or alloys to produce products having improvedsurface character istics. The invention is also applicable to theextrusion of billets and/or ingots made from soft metals and/or alloys,e.g., lead, tin, aluminum, brass, etc., to provide extruded productshaving improved surface characteristics. In the extrusion of either typeof metal, the invention provides the advantage that the annular skin ofmetal removed from the workpiece is easily removed from the product andno difiiculty is encountered in removing the skin from the extrusiontools. As mentioned hereinbefore, hard, refractory metals and alloysinclude the metals nickel, chromium and cobalt and alloys thereof suchas nickel-chromium alloys, nickel-chromium-iron alloys,nickel-chromium-cobalt alloys, cobalt-chromium alloys, stainless andheat-resisting steels, etc. As is known, such alloys often containrelatively substantial amounts of other alloying elements such as,aluminum, titanium, tungsten, vanadium, molybdenum, columbium, silicon,manganese, etc. Copper, copper-base alloys, mild steel, etc., may alsobe satisfactorily extruded in accordance with the invention.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications andvariations may be resorted to without departing from the spirit andscope of the invention, as those skilled in the art will readilyunderstand. For example, a plurality of product die orifices may beemployed, if so desired. Such modifications and variations areconsidered to be within the purview and scope of the invention andappended claims.

I claim:

1. An extrusion apparatus for extruding solid hard refractory metalwhile simultaneously extruding surface defects therefrom which comprisesan open end extrusion container of constant internal diameter andadapted to receive metal to be extruded, a concentric die assembly atone end of the container and comprised of a die structure formed of anouter annular die and a substantially concentric axially movable innerproduct die maintained in fixed position during extrusion, the outer diebeing cooperatively positioned in concentric relationship to the innerdie such that the inner wall of the outer die and the outer wall of theinner die form therebetween a continuous and uninterrupted annular diescalping orifice independent of the container and adapted to extrudesurface-defective metal, said inner die and outer die being positionedoutside the container with the outer die being separate from but inabutting relation with the container and having at the plane of abutmentan internal diameter which is the same as the diameter of the inner wallof the container, an axially movable die holder in engagement with theinner product die, and an axially movable annular die block inengagement with the die holder and having an annular passage therein incommunication with the annular die orifice to receive extrudedsurfacedefective material from the annular die orifice, whereby whenhard refractory metal is extruded the surface defects thereof passthrough the annular die orifice while the desired solid extruded productsimultaneously passes through the product die.

2. An extrusion apparatus for extruding solid hard refractory metalwhile simultaneously extruding surface defects therefrom comprising, incombination, an open end container of constant internal diameter andadapted to receive metal to be extruded, a concentric die assembly atone end of the container and comprised of a die structure formed of anouter annular die and a substantially concentric axially movable innerproduct die maintained in fixed position during extrusion, the outer diebeing cooperatively positioned in concentric relationship to the innerdie such that the inner wall of the outer die and the outer wall of theinner die form therebetween a continuous and uninterrupted annularscalping die orifice independent of the container and adapted to extrudesurface-defective metal, said inner die and outer die being positionedoutside the container with the outer die being separate from but inabutting relation with the container and having at the plane of abutmentan internal diameter which is the same as the diameter of the inner wallof said container, an axially movable die holder in engagement with theinner product die, an axially movable annular die block in engagementwith the die holder and having an annular passage therein incommunication with said annular die orifice to receive extrudedsurface-defective metal from the annular die orifice, a holding devicecomprised of slidably opposed supporting blocks engaging the annular dieblock to substantially prevent relative movement between the dieassembly and container during extrusion, a retractable member movableaxially to the container and being in engagement with the annular dieblock and adapted to simultaneously withdraw the solid extruded product,the surface-defective material and discard metal to a position away fromthe container subsequent to the extrusion operation, a power device forwithdrawing the retractable member to a desired position away from saidcontainer, a gripping device comprised of slidably opposed members forholding the withdrawn solid extruded metal, surface-defective metal anddiscard metal in a relatively fixed position, and a cutting deviceadapted to simultaneously separate the solid extruded metal from thesurface-defective metal and from the discard metal in a single cuttingoperation.

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